The invention relates to a pneumatic dispatch station with a connecting tube mounted within a station housing for alignment with a forwarding tube entering the station housing from above and one entering from below, said connecting tube being selectively coverable or releasable at one end by means of a slide seated in a slide housing, the slide location being bypassed or bridged by means of a valve-controlled air conduit, and said connecting tube being movable to a position with its upper end in alignment with a transmission tube inserted into the upper limiting surface of the station housing and equipped with a restraining device for pneumatic travelers which are to be dispatched and being movable to a position with its lower end in the area of a receiving opening in the lower limiting surface of the station housing.
In a known pneumatic dispatch station of this type--German OS No. 29 05 994 (FIG. 1 and claims 1 and 5)--, the connecting tube is displaceable perpendicular to its longitudinal axis. Both the forwarding tube entering the station housing from the top as well as from the bottom exhibit openings which lead into an air channel via which the two forwarding tube sections are connected to one another. A clack valve working in one direction is situated in this air channel. A slide housing is disposed in the lower edge area of the connecting tube, a slide being perpendicularly displaceable relative to the longitudinal axis of the traveling tube path within said slide housing in such manner that the lower end of the connecting tube can be optionally covered (blocked) or released. For the reception of an incoming pneumatic traveler, the slide is inserted into the connecting tube; therewith, the incoming pneumatic traveler slides down against the slide pneumatically decelerated. After the shutdown of the pneumatic conveyor, the connecting tube is displaced so that its longitudinal axis remains parallel to its original orientation until it is in alignent with the outward transfer opening. Thereupon, the slide is retracted so that the pneumatic traveler can fall through the outward transfer opening into a collecting container. Subsequently, the connecting tube is returned into the transit position.
The aligning position of the traveling tube with the outward transfer opening simultaneously corresponds to the aligning position of the connecting tube with the dispatch tube. A pneumatic traveler intended for dispatch cannot yet be introduced into the dispatch tube given an aligned position of the connecting tube with said dispatch tube since the lower end area of the dispatch tube is blocked by means of a switchable restraining device. The acceptance of a pneumatic traveler ensures only after the outward transfer of the received pneumatic traveler and a subsequent, renewed closing of the lower edge area of the connecting tube by the slide.
The invention proceeds from a variation of the known pneumatic dispatch station insofar as the slide is disposed not in the lower area of the connecting tube but, rather, at the upper end of the connecting tube. Pneumatic travelers intended for reception, therefore, must always enter the pneumatic dispatch station from below and come to rest with their upper end face in the area of the slide, this position of rest being made possible by means of maintaining the device via the valve-controlled shunt air conduit. Pneumatic travelers which first enter the pneumatic dispatch station from the top are transferred out by means of keeping the connecting tube free over the location of the pneumatic dispatch station; after leaving the station area, the direction of the driving air is reversed and the pneumatic traveler is conveyed back to the pneumatic dispatch station from below. This variation of the known pneumatic dispatch station is connected therewith so that particularly heavy pneumatic travelers and pneumatic travelers transported with a high air speed enter the pneumatic dispatch station more slowly from below in the described reception and, thus, more favorable operating conditions exist both in view of the mechanical loads of the station as well as in view of noise propagation.
A pneumatic dispatch station with a slide in the upper area of the pneumatic dispatch station which can likewise be employed as a dispatch, receiving or transit station is already known from the German LP No. 19 08 766 (FIG. 9 as well as specification col. 10, line 65 through col. 11, line 32). The essential connecting element of this pneumatic dispatch station is a shunt tube which is rotatably mounted at its upper area and can be placed in alignment with the second forwarding tube or with an outward transfer opening at its lower end. The slide is situated directly above the pivot bearing of the shunt tube. For receiving a pneumatic traveler, the shunt tube remains in alignment with the two forwarding tube sections connecting with the station housing; the slide is inserted into the upper forwarding tube path. A pneumatic traveler arriving from below is thus pneumatically decelerated and arrives at the slide with a very low final velocity. Pneumatic travelers which are to be sent out can be inserted into the open end of the lower forwarding tube after the shunt tube has been pivoted into its outward transfer position; likewise, a pneumatic traveler to be dispatched can be directly introduced into the shunt tube when said shunt tube is in its pivoted-out state, whereby there is no longer any possibility here of keeping a further pneumatic traveler which is to be dispatched in readiness within the pneumatic dispatch station during the outward transfer of a pneumatic traveler or of already dispatching said further pneumatic traveler. The possibility of introducing a pneumatic traveler into the station from below through the outward transfer opening also exists; a holding device secured to the shunt tube thereby accepts the pneumatic traveler and, given an appropriate pivoting of the shunt tube, conveys it via the lower forwarding tube opening. Thus, in addition to the transit position and the outward transfer position, the shunt tube must be able to assume a third basic position in which pneumatic travelers which are to be dispatched are introduced into the forwarding tube path. Beyond that, it is structurally difficult to secure the pneuamtic traveler in the holding device and to prevent it from dropping immediately out of the introduction opening on the one hand and, on the other hand, to render possible an unimpeded dropping-out of the pneumatic traveler given an aligned position of the holding device with the lower forwarding tube. These conditions can be met in practice only with additional control-engineering outlay and/or loss of simplicity of operability of the pneumatic dispatch station.